Cailiao Baohu (Feb 2022)

Study on Corrosion Resistance of Cationic Waterborne Acrylic Coating

  • ZHU Kang, FAN Wan-xin, HUAN Jia-qi, ZHANG Xiao-ya, SUN Ying, HU He-feng

DOI
https://doi.org/10.16577/j.issn.1001-1560.2022.0038
Journal volume & issue
Vol. 55, no. 2
pp. 54 – 59

Abstract

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Aiming at understanding the corrosion resistance of siloxane hydrolyzate cured cationic waterborne acrylic coatings, waterborne metal anti-corrosive coatings were prepared by cationic hydroxy acrylic resin dispersion containing tertiary amine group cured by siloxane hydrolysate WKHY-601.With using DSC, TGA, FT-IR and CHI660E electrochemical workstation, the curing mechanism of the coating and the main factors affecting its salt corrosion resistance were researched systematically.Results showed that the curing of the coating was achieved by the reaction of the silanol hydroxyl group and the alcohol hydroxyl group in the resin and the self-condensation of the siloxane hydrolyzate to form a cross-linked network.The content and type of the tertiary amine group in the resin and the amount of the curing agent siloxane hydrolyzate influenced the salt corrosion resistance of the coating film.As the content of tertiary amine groups increased, the self-corrosion potential of coating increased and the self-corrosion current density of coating declined.After reaching a certain level of the content of tertiary amine groups, the value remained stable.Besides, the dimethyl type tertiary amine group with less steric hindrance was better than the diethyl type, and the increase in the amount of siloxane hydrolyzate was beneficial to improve the compactness of the coating film and enhance its salt corrosion resistance.When the amount of siloxane hydrolyzate was excessive, the content of tertiary amine groups in the coating film would decrease, resulting in weakening the salt corrosion resistance.Furthermore, the self-corrosion potential of the coating sample prepared by DM type resin with a tertiary amine group content of 0.42 mmol/g and siloxane hydrolysate WKHY-601 according to a mass ratio of 3∶1 was as high as-0.298 V, and the self-corrosion current density was only 1.308×10-9 A/cm2, performing excellent salt corrosion resistance.

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